Power supplies are employed with electrical equipment to provide a stable output voltage. Electrical power equipment typically requires a direct current voltage supply. However, electricity is typically supplied through an alternating current (AC) distribution. A power supply may be an alternating current-direct current (AC/DC) power supply. A power supply may be utilized to convert an AC source, such as from power mains to a DC output which may be utilized to power components of an apparatus or system. For example, an AC/DC power supply may receive a 110 volt alternating current (VAC), 60 Hertz supply from mains, such as from a wall plug or power outlet. An AC/DC power supply may convert the AC supply to a DC output, such as a 5 volt or 12 volt DC output. The components of an electrical device may be powered through connection to the DC output, directly from the power supply or through a power bus.
In order to reduce the power consumption of a power supply, the power supply may be designed to operate at a high efficiency. Power supply efficiency may refer to the DC output of a power supply divided by the AC input. When the power supplies draws more AC power to produce the same DC output, the efficiency is reduced. The reduced efficiency of a power supply causes an increase in power consumption to handle the load.
When a narrow load range is required for a power supply, the power supply may be designed to operate efficiently. However, many applications of electrical equipment require a wide load range. A problem associated with conventional power supplies is the reduced efficiency of the power supply at light loads. For example, efficiency may be 75-90% at 50-100% of the maximum specified load of the power supply. However, efficiency at loads less than 50% of the maximum supplied load is poor.
Redundant power supplies for network storage systems typically operate at 30-35% of the maximum supplied load. With an increase in energy costs, the cost associated with supplying power for redundant power supplies has become significant. Consequently, a method and system for increasing the efficiency of power supplies is necessary.